2017 Volume 66 Issue 9 Pages 644-647
The surface flatness of photo-curable polysilsesquioxane (PSQ) films for gate dielectric layers of pentacene thin film transistors (TFTs) was considerably improved by ultra-violet light (UV)/O3 treatment; the root-mean-squared (RMS) roughness was improved from 0.35 to 0.23 nm after 40-minute treatment. However, the PSQ surfaces became hydrophilic because hydroxyl groups, which degraded transistor performances, replaced the organic functional groups such as methyl groups by the UV/O3 treatment. Therefore, 1,1,1,3,3,3-hexamethyldisilazane (HMDS) treatment was successively performed after the UV/O3 treatment to replace the hydroxyl groups with hydrophobic silyl groups. It was found that four-hour HMDS treatment under dry nitrogen was enough to reduce off current of pentacene TFTs. As a result, the carrier mobility of the pentacene TFT fabricated with UV/O3 and HMDS-treated PSQ layers became 0.59 cm2V-1s-1, which was more than seven times higher than that of the pentacene TFTs with untreated PSQ layers.
